Spectators at a Cape Town beach in South Africa over the weekend were horrified to see nineteen pilot whales wash up on shore, ultimately resulting in the deaths of seven of the huge sea creatures.

Officials at the National Sea Rescue Institute were puzzled as to why such a large group of whales would beach themselves all at once, but were determined to do everything possible to try and save the remaining 12 whales. Pilot whales, related to dolphins, often grow as large as 20 feet in length.

“We don’t know what might have caused the mass whale stranding, unfortunately seven have died,” said Craig Lambinon, the spokesman for the National Sea Rescue Institute.

Rescuers at Noordhoek Beach were kept busy frantically hosing down the surviving pilot whales with water while the dead carcasses were collected for disposal and the remaining living whales were being directed to get back into deeper water in order to return to the sea. One of the reasons that whales beach themselves is when their natural sonar becomes disoriented if they swim into waters that are too shallow.